Process for the production of anhydrous magnesium chlorid or anhydrous double chlorids of magnesium



E. A. ASHCROF.

PROCESS FOR THE FRODUCUON F'ANHYDRUUS MAGNESIUM CHLRID GE ANHYDEOUSDUUBLE CHLORIDS 0F MAGNESIJM. AHUCATIGM FILED Aue. l2, 19m RENEWED om.9.

2. .E Mal m 'Zvw P m Z m my.

E.y A. ASHCROFT.

PROCESS FOR THE PRODUCTION 0F ANHYDROUS MAGNESIUM CHLORID 0R ANHYDROUSDOUBLE CHLORIDS 0F MAGNESIUM. l

APPLICATION FILED AUG. I2. 1919. RENEwEUocT. 9. |920A 1,359,652.` lymanned Nov. 23,1920.

3 SHEETS-SHEET 2.

E. A.:ASHCROFT. PROCESS FOR THE PRODUCTION OF ANHYOROus MAGNESIUMOHLORIO OR ANHYDOus DOUBLE OHLORIOS OF MAGNESIUM.

APPLICATION FILED AUG.I2, 15H9. RENEWED OCT. 9. 1920 1,359,652. PatentedN0v.23,1920.

' h3 SHEETS-SHUT 3.

i 'STATES f-GFFICE? Encan ARTHUR Asircnori, di* LoNDoN, ENGDAND;

Appi'ieauon ined august 12,' 191e', sensi No, 317,082.Jzseaeygealoeiober e, i920. serial No. 415,951'.

- Tio all may concern:

Beit known-that'l, EneAaAnrHuii Asia:- ciioirr, a subject oi the King ofGreat Britaln resid at 65 London Wall, in the cityl of liondon, ngland,have invented new and' useful, improved Processes for the Production ofAnhydrous Magnesium f chia-id, Oli-Anhydrous Dottie chinees 'Qi-Magnesium', of which -thefollowing is Va invention relatie-@principallyto the proiliitionof anhydrous magnesium chlo lrid more especially from'the ordinaryhydratedfm'agnesium chlorid of .'comnierce, which saltcrystallizes from" its solutions containin the removalo waterofhydrationby ordinary lheat processes is attended by seriousdiiiiculties and that dehydration cannot be 'eii'ected by any linownprocess, available fori commercial purposes, the processes hithertoemployed having1 been attended by serious decomposition -ot the neutralsalt, loss 'of acid, and formation of basic residues.

From Afl). 1870 tov Aj. DI"1890`, or therevabout, manv'attempts weremade to de- A' duction o iSolvay and others) more particularly with aview toiproviding processes for thepro- 'chlorin from the ma nesiumchlorid of the 'Stassffurt deposits. n those processes itfhas, atvarious times, been sncf- .gested to use currents clair (hot, or cold orof other ases includinohydrochloric acid as, the latter havingz beensuggested for t e purpose o' -improvingth .-eq'uilialso been proposed toraiseythe temperature brium lconditions according .to 'tie well knownlaws or mass reactions andit has ofthe salt progressively duringtreatment to avoid fusion' and therefore .indo not claim theseoperations tobe novel separately con- A sidered,`although l inalie useof themtiiej process according to' my present invention..

'ln spite oi? the aforesaid attempts and the considerable amount ofworlrdone at A of themwere complete, or 4successful, from l a practicalpoint-civica", because, throughv six molecular proportions of.-water'f'of ydration. lt is well lmown that troublesome operation), andin more recent years bythe treatment, with chlorin as, of

converter.

l' have invented novel means whereby the water of hydration can beentirely removed' .from hydrated magnesium chlorid without rnonucrioN orANHYD'noUs riAeNE'siuMcHDomD oit ANi-iy.- i I .Ditous DOUBLE oHLoiiiDsor MAeNiisiUM. f

'spetmeaunn of Lettersintent i Patented Nov. 23,1920.

diiiiculty, and. at but small cost. According to my invention I employthe magnesium chloridin a suitable form as hereafter ex-y plained(preferably as needle crystalsyandf after removing'.suilicientl of theAwater 'of hydration byv'means of 1a voluminous current of heated air,which raises., the fusion ointl of the salt to above 250- centigrade,

treat the partically 'dehydrated 'crystals-- with a slow current ofhydrochloric acid gas which vneed only be used 'in` suflicient quantityto combine with the waterliberated from the crystals, 'forming astrong'A solution thereof which is afterward completely re. I covered.;During the said treatment with .hydrochharie acid gas the vessel orretort, in` which the treatment takes place should be externally heated,and the temperature i should be slowly raised fromv a minimum oi 150centigrade, orthereabout, to a maxi- -that fusion does not take place atany eriod of the treatment, but incipient tusionis produced toward theend of the said treatment and the material leaving the ap- 'mum or 650centigrade, or thereabout, so

paratus then" assumes a partially crystalline formand consists ofmagnesium chlori'd 'of a very high degree oi purity, 98 to 99 percent.magnesium chlorid being possibleV if care be exercised in the operation.

-During the preliminary drying i with voluminous current of heated airthe whole as this will prevent the usion or the 'charge o'l. the heatlis moet conveniently imparted tothe 'charge by heatin the air employed,100 l which otherwise would take place. too' l readilyn When from threeto tour molecular. proportions oil vwelter, out ci the total con-f tentof sin Amolecular proportions, have been removed from the salt themelting` point Awill be raised from about 80 cent1- iet grade, orthereabouajto about 250o` conti-` -a fused bathv ofthe initial compounin a I sol ' however, the dehydration by means of air tion of the salt,and therefore no loss of the chlorin content, will have taken place.vIf,

be pushed much further partial decomposition will ensue with evolutionof hydrochloric acid gas.

Therefore, at this stage, a slow current of hydrochloric acidgas issubstituted for the air current, and thereafter the temperatureissteadily raised as the water is removed from the charge.

I'have found that the action of the hy-l drochloric acid gas under thesecircumstances is not merely an improvement of the equilibrium condition,but 1s that of a powerful desiccator, and this to such an extent thatvery shortly after the application of the hydrochloric acid gas to thecharge, and

at a temperature very little above 250D centigrade, the greater part ofthe water of hydration has been completely removed and carried overinto'the condensing apparatus in the form of a strongsolution ofhydrochloric acid. This solution condenses, .con-

taining about 2O per cent. hydrochloric acid. Thereafter, on continuingthe same current of hydrochloric acid gas, while the charge 1s slowlyraised to the maximum temperature of 650o centigrade, the remainder ofthe water-is carried over from the charge and, together with it, anexcess of dry hydrochloric acidgas, which, as hereinafter eX'- plained,is immediately absorbed in the Water and partially saturated solutionpassinggthrough the absorbing apparatus.

y this means the whole of the hydrochloric acid gas employed in thistreatment is recovered in the form of a strong solution containing say33 per cent. of hydrochloric acid, and lcan be used again and again forthe treatment of subsequent charges by expelling the gas by means ofconcentrated sulfuric acid, which also can be used again and again byreconcentrating the said sulfurie acid. Y

By this means it is found necessary to employ only a quantity of acidnearly equivalent to the weight ofthe salt underA treatment, such acid,as hereinbefore stated,

being completely recovered and available retorts, the discharge of whichis continu-` Vous, land the charging of which may be inrceeding 50,000cubic feet per hour per ton of charge, although it may be very much lgreater, say as much as 500,000 cubic feet.

This stage is preferably carried on until such an amount (usually onethird, or thereabout) of the total water has been removed from theinitial material, so that the melting point is raised to say 250Ocentigrade,

or thereabout, no loss of chlorin from 'the salt ocurring. It mayhowever (if preferred for any reason) be carried further, somehydrochloric acid then being given off and some magnesium oXid, oroxy'chlorid, remainingin the charge. In such case the subsequenttreatment with hydrochloric acid will correct this effect and ,restorethe neutrality of the salt, but with 'a corresponding consumption ofhydroc loric acid gas.

In the second stagel of the process, treatment with a small, or slow,currentof hydrochloric acid gas is substituted for treatment with heatedair (in the same, or another. vessel) and heat is applied Ato thecharge, allowing sufficient time for fthe small, or Slow, current ofhydrochloric acid gas to remove the reniaining water withoutdecomposition of the salt, the temperature being slowly raised to say650o centigrade. By this treatment a product having'98 per cent., ormore, of pure anhydrous magnesium chlorid can be readily obtained. The

product is white and porous and remains in V105,-

that condition if the temperature does not exceed, say 5000 centigrade,but, as it is' steadily raised to about 650 centigrade, thet Aproductbecomes of a partially crystalline of weight, on fusion of the finishedproduct i,sgopsa i' 'i .it is found to be eminently suitable for theelectrolyticmanufacture of magnesium metal, or allo s. Y

'The following example is. the b est way with which I am acquainted ofcarrying out my invention in practice, but I do not limit myself to theprecise detailsof this particm4 lar example.

Stage The magnesium c hlord is. pre-A pared in the form of needlecrystals, which can conveniently bedone by allowing a solution,concentrated to a strength of about-80 Twaddell (1.400 specificgravity), to cool,

from say 50 centigrade to atmospherlc temperature, when more than halfof the magnesium chlorid content will crystalline out and the crystalsmay be centrifugaled, orl drained, -in any suitable manner, and thenbeplaced in the air drying apparatus and subjected to the aforesaidvoluminous current of dry air at a temperature whichl must be lower thanthe fusion point ofthe initial hydrated charge, to commence with; forinstance, in the case Wherev the heated air is passed in an upwarddirection incontact with'a descending charge, the air may be admitted atabout 150 centigradc, and it will cool as it ascends until the incomingcharge is met by air" at a temperature -low enough to prevent itsfusion, but the air may, as the charge dries, be rather more stronglyheated, say' up to 250 centigrade, the object of these regulations beingin any case that the crystals shall not be caused'to fuse at any stageof the treatment but shall retain their form and dimensionsnotwithstanding the greatA loss of weight.

. The aforesaid conditions are automatically i brought about if anapparatus ha ving a (ontinuous discharge, as hereinafter described andillustrated, be employed, because, in thatvcase, the coolerair near theexit therefor from the apparatus will partially dry the descendingcharge, which,l in its turn, will be subjected to the hotter air at thelower part of the apparatus. ln such an np3 i paratus it is convenientto heat the air' to a higher degree, say up to '300' centigrade..

In the accompanying drawingsn Figure l represents in vertical sectionyanapparatus suitable' for use in carrying out the irst stage of theprocess;

Fig. 2 shows in vertical sectien an appa-i y ratus suitable for -use 1ncarrying out 55 the second stage ofthe process; and hig. 3 is a more .orless diagrammatic elevation oi a complete installation torcarrying outthe process.

The apparatus shownin Fig. l comprises a'vertical retort A, of iron, orother suitable metal, which may be enameled inside and is so'set as tobe capable of retaining the heaty which is imparted to the charge bymeans of the heated air. This is shown as being done by surrounding-theretort by a casing B, containing a non-conductor ofheat Vsuch asslag-Wool. v y t The current 'ofy air is preferably intro- "duced atthelower end of the retort and, in

the drawing, this is shown as bei effected' by forming theoutlet intwo'parts ,and D, -the part C dipping somewhatinto Vthe part D, with agap abetween, this gap being surrounded byzan air lchannel E into whichheated air is passed by the inlet Efrom any suitable source. The airpasses up'throu h the descending charge and escapes at' 2,

'at d2 Jforming an air-tight joint, F is a 'while the treated materialdescendsinto any i suitable receptacle, such as a churn, whose .upperedge may lit 'against a resilient ring ribbed, or star, dischargingwheel, the speed of rotation 'of which can be regulated, by

any, convenient means between say one `and sixteen revolutions perminute.l During the air `treatment it is convenient to desiccate theingoing air, as, by this means, a somewhat better result-is obtained.Desiccation of the air however is not essential.l l have shown, at theupper end vci the retort A, a large cover a, orcleaning purposes' Aand asmaller cover a2 for charging purposes, both of whichcan be sealedair-tightly. The

lretort may also beV charged continuously, but

l prefer to introduce the charge intermittently, periodically removingthe small door a2, -or that purpose, as the level of-the material in theretort falls.

Instead `of the aforesaid apparatus lv may v employ a similar apparatuswhich is charged anddischarged in hatches,ra grating being providedunderneath for distributing the `carried too far, irst an evolution ci'hydrochloric acid gas talles place due to" the decomposition of thesaltat the high temper-v ature necessary for expellingv the bulk of thewater of hydration, and finally, when the salt is nearly 'dry and thetemperature has reached 200 to 250 centigrade an evolution of ,ehlorinwilly take place. lt is neither necessary, nor desirable,' to carry thetreatment so tar.

li' therefor now vproceed to the second stage of the process: i

Stage 2:-1This may be carried out in the same lapparatus as that inwhich the irst' stage of the process is carried out, or in anothervessel, or retort, which may be similar to it with ,the difference thatmeans are provided for heating .the charge to a tem# perature of 650centigrade, or thereabout.

When the operation is carried out in the same vessel, or retort, fluesare preferably provided around it for the purpose of this heating and,immediately afterthe treatment, according to the first stage, with avoluminous and rapid current of air, treatment by a slow current of dryhydrochloric acid gas is substituted for the air treatment, and heat-isapplied'so as to slowly raise the temperature to 650 centigrade, orthereabout. As the hydrochloric acid gas has a strong aiiinity for waterit will rapidly abn sorb the water of the charge while not causL ing anydecomposition of the magnesium chlorid and, on leaving the hot vessel,or

retort, the moisture at once condenses and can be collected inthe'condition'of a strong a separate apparatus and to arrange it thatthe material continuously discharged from the apparatus of the iirststage of the treatment is intermittently introduced into the apparatusfor the second stage of the treatment and then is continuouslydischarged from the last named apparatus. Y

Fig. 2 of the accompanying drawing lshows in vertical section a suitableapparatus which I have devised for this purpose. rl`he retort is shownas consisting of a bodypart G, made in two sections, and an upper partconsisting of a closed hopper H, with a large cover h for cleaningpurposes and a small cover 7b2. for charging and also an outlet Ifurnished with a discharge screw not 4shown into which outlet adepending part g projects and leaves a space at g2 into whichhydrochloric acid gas passes by the pipe g3 and thence passes up throughthe descending charge and (accompanied by water vapor), away at h3, toany suitable place of discharge. The body-part G, depending part g,"andhopper and discharge parts (H and I) may be made of any suitablematerial.` For instance the body-part 'and depending part may be made ofsilicaglass and the hopper and discharge Vparts may be made of iron,enameled internally.

The heating of the retort is shown as being effected by ay furnace J,surrounding the body-part G, and heated by gas and air admitted at anysuitable points, such as are shown for instance at K, the products ofcombustion passing ofi' by the chimney J2.

This treatment with the hydrochloric gas may continue for say three, orfour, hours, p during which time the vaporized solution of hydrochloricacid will distil over at h3, and can, after condensation, drip throughav sight-tube into a vessel provided for its retention, surplushydrochloric acid gas being simultaneously absorbed in water inthe-absorber. The hydrochloric acid absorber may consist of a series oflVoulfes bottles, or jars, terminating' in a tower of small diameterpacked with any suitable packing and supplied with water.' By means ofthe sight-drip, and of a graduated vessel provided for receiving theacid, the progress throughout the period of .the treatment can beaccurately observed which is very convenient in practice.

After the aforesaid treatment the chlorid will contain fromninety-eight, to ninetynine, per cent.` of pure magnesium chlorid andmay be either fused to a dense crystalline snow-white, or water-white,salt, or

be used directly for any required purpose; for instance, it may be usedin electrolytic cells for the production of magnesium and chlorid. Thetreated material is discharged into any suitable receptacle, and whereinany caked lumps, due to incipient fusion, are broken up, while beingdischarged.

Double salts of'magnesium chlorid; such,

for instance as carnallite, (the double chlohydrochloric acid employedis recovered,

for should even a small portion of acid be removed from the salt duringthe air treatf ment this can be readily absorbed by bubbling theescaping air through vessels containing water, and the dilute-solutionof acid thus obtained can be employed in the absorbing apparatus for thehydrochloric acid plant. It will however iusually be found preferable tostop the air treatment before any acid has been liberated.

An example of a suitable arrangement of apparatus for the carrying outof my. process is illustrated on Fig. 3, which shows in outline anarrangement ofthe plant, in a building of two floors, the lower floorcontaining a pressure blower l the air from jectionable umes.

present) and escapes, while the charge of partially dried magnesiumchlorid is again taken to the upper floor and charged, through a secondhopper at 6LL into the continuously discharged aciddrier 6 from whichthe finished anhydrous magnesium chlorid produced may be continuouslydischarged into any suitable vessel. The hydrochloric acid generator 7furnishes gaseous hydrochloric acidfor this acid-drier 6, which gas,after passing through the charge, escapes accompanied by the watereliminated from the crystals and is condensed, in the absorber plant 8,to a nearly saturated solution of hydrochloric acid for reuse, only'sufficient water being supplied to the small tower 8a of the absorbingplant 8 to produce a concentrated solution from all the hydrochloricacid which is absorbed. In the generator 7 concentrated sulfuric acid isused to again liberate the hydrochloric acid gas, the acid being used atapproximately 1.840 specic gravity and discharged from the appa.

ratus at approximately 1.560 specific gravity, at which strength it willbe found to contain only approximately three-tenths of one per cent. ofhydrochloric acid. 7EL is a tank for hydrochloric acid and 7b iS a tankfor.

sulfuric acid. The generator is preferably worked warm (say about 90ocentigrade) and a current of air may be employed to expel the last ofthe hydrochloric acid so that the sulfuric acid can be againconcentrated; for instance, in an ordinary cascade concentrator withoutthe production of ob- This operation is very readily carried out. Twogenerators worked alternately maybe provided for each retort.

The process in accordance with my invention is very convenient andeconomical for use in conjunction with the process described in thespecification of my application Ser. No. 317084 for Letters Patent, (ofeven date herewith) for the simultaneous production of metallicmagnesium or its alloys and magnesium chlorate, which in turn isutilized for the production ofi other by-products, the material producedby my invention being eminentlysuitable for my improved electrolyt'icprocess described in the specification of my. application Ser. No.317803 for Letters Patent of even date herewith. What I cla-im is 1. Inprocesses for the manufacture of any raised to above 250o centigrade andafterward applying a slow current of hydrochloric acid 'gas to' absorband remove the remaining water of hydration.

2. In a process in accordance with claim 1; the removal of a portion ofthe water of hydration by a voluminous current of heated air andfollowing such treatment by the application of a slow current ofhydrochloric acid gas, substantially as hereinbefore described.

3. rIhe process in accordance with claim 1, the said process consistingin subjecting hydrated magnesium chlorid to a partial dehydratingprocess by means of heated air without applying external heat to thecharge, completing the dehydrating by meansk of a slow current ofhydrochloric acid gas, with the application of external heat to carryingout the first stage of thev process only until such amount of water hasbeen removed from the initial material that the fusion point is raisedto 250o centigrade, or thereabout, and no hydrochloric acid has beenliberated.

6. In a process in accordance with claim 1, effecting the preliminarypartial dehydration of the hydrated compound by means of a voluminouscurrent of air in desiccated condition.

7. In a process in accordance with claim 1, effecting the preliminarypartial dehydration of the hydrated compound by means of a voluminouscurrent of air, halting said dehydration by the current of air beforeany decomposition, or liberation, of the hydrochloric acid has takenplace, and thereafter employing the hydrochloric acid utilized for themain part of the'drying process in a cyclic manner by absorbing in waterthe acid which 'escapes from the generator to form a strong solutioncontaining all the acid employed and expelling the dry hydrochloric acidfrom this solution by means of sulfuric acid, substantially ashereinbefore described. In testimony whereof I have signed my name tothis specification in the presence of two subscribing witnesses.

EDGAR' ARTHUR ASHCROFT. Witnesses:

G. F. TYRoN, L. WALTER.

